Lightning strikes the house next door, and echoes off the houses and hills of the neighbourhood. Sennheiser MD421 pointed at open window during thunderstorm, Ampex MX10 tube mixer, Ampex 960 tube reel-to-reel. Dual mono recording, good fidelity. Tape hiss is masked by white noise from rain. If you listen closely, the leading edge of the clap is preceded by a faint click (visible in audio editing software), which is likely the instant the bolt makes contact and sends electricity through everything in the vicinity (tubes are forgiving). The shockwave from the superheated air (which only travels at the speed of sound) arrives as the main clap a split second afterwards. Startled recordist can also be heard in the fadeout.